1. Field of the Invention
This invention relates to a stable blood serum reference composition capable of use as a blood serum reference control or a blood serum reference standard and to a method of preparation and use thereof.
2. Description of the Prior Art
There are several electrolytes in serum that must be examined in order to determine the health of a patient. These electrolytes are sodium and potassium (which possess a positive charge) and chloride and bicarbonate (which possess a negative charge).
Bicarbonate and carbon dioxide are interrelated by the following equation: EQU H.sub.2 O+CO.sub.2 .revreaction.H.sub.2 CO.sub.3 .revreaction.H.sup.+ +HCO.sub.3.sup.-
Therefore, clinical laboratories sometimes assay for carbon dioxide instead of bicarbonate.
Most control serums currently used in clinical laboratories contain all of these electrolytes for calibration purposes.
One prior art blood serum reference standard is described in U.S. Pat. No. 3,466,246 (hereinafter referred to as Anderson), said patent being incorporated herein in toto by reference. Anderson discloses a stable blood serum reference standard having a standard carbon dioxide content wherein a freeze-dried blood serum component of the reference standard is reconstituted with an aqueous ammonium bicarbonate component of the reference standard. The blood serum reference standard disclosed by Anderson is undesirable because of the myriad problems encountered due to the presence of the ammonium ion therein. For example, the ammonium ion contaminates solid state potassium and sodium electrodes as well as interferes with various clinical procedures such as the Berthlot reaction for urea nitrogen and the glutamic dehydrogenase reaction for urea nitrogen. In addition, excess ammonium ions also inhibit various enzymes, e.g., urease.
Another reference standard blood serum for the calibration of automatic blood serum analyzing apparatus is disclosed in U.S. Pat. No. 3,629,142 (hereinafter referred to as Marbach), said patent also being incorporated in toto by reference. The reference standard blood serum of Marbach contains trihydroxymethylamine (Tris) carbonate so as to permit it to be reconstituted just prior to use with distilled water so as to restore a predetermined carbon dioxide level in the reference serum. Although the reference standard blood serum of Marbach overcomes several of the problems inherent in Anderson's blood serum reference standard (see Marbach, column 2, lines 25-48), the amine group sticking off the Tris employed in Marbach's reference standard acts as a competitive inhibitor of urease and thereby also interferes in various clinical assays.